Expansion anchors are disclosed, for example, in European patent application EP 0514342 A1. They are inserted into a hole drilled in a substrate, for instance, a wall or ceiling of a structure. When an expansion cone that is arranged on the stud and that has a slanted surface is pulled into an expansion element configured as an expansion sleeve, this expansion element is widened radially and pushed outwards, thereby anchoring the expansion anchor in the substrate. According to EP 0514342 A1, a friction-reducing coating is provided on the contact surface between the stud and the expansion element.
U.S. Pat. Appln. No. 2008/050195 A describes an expansion anchor in which the surface roughness of the expansion sleeve increases towards the rear end of the anchor.
European patent application EP 0567203 A2 discloses a rolling method in which an anisotropic coefficient of friction is generated by texturing the roller surface.